Nonaqueous electrolyte secondary cells and process for fabricating same

Abstract

A nonaqueous electrolyte secondary cell includes a rolled-up electrode unit composed of a positive electrode, a negative electrode and a separator interposed therebetween, and a negative electrode current collector plate and a positive electrode current collector plate joined to the respective ends of the electrode unit. The collector plate has a two-layer structure comprising a copper layer made of copper or an alloy consisting predominantly of copper, and a metal layer made of a metal not forming an intermetallic compound with lithium and having a lower laser beam reflectivity than copper or an alloy consisting predominantly of the metal. The collector plate has its copper layer contacted with an edge of the negative electrode projecting at one of the opposite ends of the electrode unit and welded thereto with a laser beam.

What is claimed is:  
     
       1. A nonaqueous electrolyte secondary cell comprising an electrode unit ( 2 ) encased in a battery can and comprising a positive electrode ( 23 ) and a negative electrode ( 21 ) each in the form of a strip and a separator ( 22 ) interposed between the electrodes, the cell being adapted to deliver electric power generated by the electrode unit ( 2 ) to the outside via a positive terminal portion and a negative terminal portion which are provided on the container, a negative electrode current collector plate ( 3 ) comprising a plurality of layers including a copper layer ( 31 ) made of copper or an alloy consisting predominantly of copper, and a metal layer made of a metal not forming an intermetallic compound with lithium and having a lower laser beam reflectivity than copper or an alloy consisting predominantly of the metal, the copper layer ( 31 ) and the metal layer forming opposite surface layers of the collector plate ( 3 ), the copper layer ( 31 ) being welded to an edge of the negative electrode ( 21 ) projecting at one of opposite ends of the electrode unit ( 2 ) in the direction of a winding axis thereof, and the negative electrode current collector plate ( 3 ) being electrically connected to the negative terminal portion. 
     
     
       2. A nonaqueous electrolyte secondary cell according to  claim 1  wherein the metal forming the metal layer of the negative electrode current collector plate ( 3 ) is nickel. 
     
     
       3. A nonaqueous electrolyte secondary cell according to  claim 1  wherein the metal forming the metal layer of the negative electrode current collector plate ( 3 ) is stainless steel. 
     
     
       4. A nonaqueous electrolyte secondary cell according to  claim 1  wherein the copper layer ( 31 ) of the negative electrode current collector plate ( 3 ) is welded to the edge of the negative electrode ( 21 ) with a laser beam. 
     
     
       5. A nonaqueous electrolyte secondary cell according to  claim 2  wherein the cooper layer ( 31 ) of the negative electrode current collector plate ( 3 ) is welded to the edge of the negative electrode ( 21 ) with a laser beam. 
     
     
       6. A nonaqueous electrolyte secondary cell according to  claim 3  wherein the copper layer ( 31 ) of the negative electrode current collector plate ( 3 ) is welded to the edge of the negative electrode ( 21 ) with a laser beam. 
     
     
       7. A nonaqueous electrolyte secondary cell according to  claim 1  wherein the negative electrode current collector plate ( 3 ) has a thickness in the range of 0.10 mm to 5.00 mm. 
     
     
       8. A nonagueous electrolyte secondary cell according to  claim 2  wherein the negative electrode current collector plate ( 3 ) has a thickness in the range of 0.10 mm to 5.00 mm. 
     
     
       9. A nonaqueous electrolyte secondary cell according to  claim 3  wherein the negative electrode current collector plate ( 3 ) has a thickness in the range of 0.10 mm to 5.00 mm. 
     
     
       10. A nonaqueous electrolyte secondary cell according to  claim 4  wherein the negative electrode current collector plate ( 3 ) has a thickness in the range of 0.10 mm to 5.00 mm. 
     
     
       11. A nonaqueous electrolyte secondary cell according to  claim 5  wherein the negative electrode current collector plate ( 3 ) has a thickness in the range of 0.10 mm to 5.00 mm. 
     
     
       12. A nonaqueous electrolyte secondary cell according to  claim 6  wherein the negative electrode current collector plate ( 3 ) has a thickness in the range of 0.10 mm to 5.00 mm. 
     
     
       13. A nonaqueous electrolyte secondary cell according to  claim 2  wherein the ratio of the thickness of the nickel layer ( 32 ) to the thickness of the negative electrode current collector plate ( 3 ) is in the range of at least 5% to not greater than 45%. 
     
     
       14. A nonaqueous electrolyte secondary cell according to  claim 3  wherein the ratio of the thickness of the stainless steel layer ( 35 ) to the thickness of the negative electrode current collector plate ( 3 ) is in the range of at least 5% to not greater than 45%.